Lithium rechargeable batteries are made from lithium metal and organic solvents, the combination of which causes fire at high temperature. The critical temperature depends on the type of batteries and the pre-cycling conditions. The lowest critical temperature is about 100.degree. C. For this reason, cell heating from abnormal conditions has to be prevented. The safety of lithium rechargeable batteries thus continues to be a major problem to be solved.
Some lithium rechargeable batteries, known in the art, have anodes made from lithium metal sheet. However these cells demonstrate a sudden rising of temperature during cycling, which occasionally results in fire. Following disassembly of the cell, it has been found that non-uniform dissolution of lithium during discharge caused an anode cut to occur near the anode tab at the end of the anode. The anode area thus became very small, which caused local heating by increased current density. The local temperature became higher than the critical temperature, resulting in fire.
It is well known to construct a lithium anode with a substrate. For example, the Japanese patent from SONY Energy Teck. (toku-gan-hei 2-51875) discloses a lithium anode with a conductive substrate to increase cell capacity. However, a lithium anode with a conductive substrate cannot completely solve the problem. To avoid disconnection of the anode tab from the Li anode during cycling, the position of the anode tab must also be considered.